Floor coverings such as carpets and rugs are prone to marks and stains. Floor coverings can be cleaned in a number of ways, which can be classified as ‘wet’ or ‘dry’ cleaning methods. Wet cleaning methods such as washing or shampooing the floor covering have the disadvantage that they can cause shrinkage of the floor covering. Dry cleaning generally involves depositing a powdered composition onto the floor covering which can readily absorb soil and contaminants from the floor covering. The powder is worked into the floor covering with the aid of a brush. Finally the dirty powder can then be removed from the floor covering by a vacuum cleaner. While such compositions are called ‘dry’, in that they flow as a powder at room temperature, they usually contain a quantity of liquid such as water or organic solvents.
The cleaning powder needs to be dispensed on to the floor covering. U.S. Pat. No. 4,268,935 and U.S. Pat. No. 5,101,532 describe powder-dispensing machines for use in cleaning carpets. In U.S. Pat. No. 5,101,532, the machine has a hopper on the front of the machine for storing dry-cleaning powder. At the front, lower part of the hopper there is a jaw which is formed by a lower flap which is hingedly fixed to the hopper. In use, the flap is oscillated about a mean gap width of around 4 mm so as to dispense powder onto the floor surface. The position of the lower flap is controlled by a user-operated control which moves the flap between one of two fixed positions: a dispense position, in which the flap is set to the 4 mm gap, and a grooming and vacuuming position in which the flap seals the hopper to prevent any powder escaping from the hopper. In use, the machine dispenses powder onto the floor surface at a controlled rate. The dispenser is designed to work well with a particular composition of dry cleaning powder, which has particular properties, such as the size of the particles. However, changes which are made to the composition of the powder, such as to improve cleaning performance of the powder, may change the physical properties of the powder which may in turn require changes to the design of the dispenser. This is undesirable for the manufacturer and for the user, who will be unable to take advantage of the improved cleaning powder without replacing their dispensing machine with a model which is more suited to the new powder. Also, while the controlled rate of dispensing powder may be generally suitable for normal use, there are occasions when a user would want to dispense a different amount of powder.